Apparatus and Method for Burning a Fuel

ABSTRACT

A novel device is described for combusting a liquid or powdered fuel having an atomizer nozzle ( 2 ), which has a valve configuration ( 41 ) for the control of the supply of the fuel, a compressed air connection ( 4 ), a mixing chamber ( 38 ) for mixing the fuel with compressed air, and a nozzle opening ( 23 ) for atomizing a mist of fuel in compressed air. A supply line ( 28 ) for the fuel and a preheating apparatus ( 5 ) are provided, which are attached in a nozzle assembly surrounding the nozzle ( 2 ). Furthermore, air channels in a sheath ( 3 ) enclosing the preheating apparatus ( 5 ) and a fastening sleeve ( 13 ) having connection channels adjoining the air channels are provided, the sheath ( 3 ) forming a ring gap ( 21 ) for the supply and heating of the compressed air with the nozzle assembly ( 12 ) of the atomizer nozzle ( 2 ). Air supply lines ( 50 ) are provided in the nozzle body ( 20 ) originating from the ring gap ( 21 ) in such a way that the valve configuration ( 41 ) is activatable by the compressed air.

The present invention is concerned with the field of combustion technology and relates to a device for combusting a liquid or powdered fuel having an atomizing nozzle, which has a valve configuration for controlling the supply of the fuel, a compressed air connection, a mixing chamber for mixing the fuel with compressed air, and a nozzle opening for atomizing a mist of fuel in compressed air. Furthermore, an apparatus is provided for preheating the fuel to a predetermined temperature, which is attached in a nozzle assembly surrounding the nozzle. The invention also relates to a method for combusting a fuel using the above-mentioned device.

PRIOR ART

Such devices are generally known in the field of combustion technology and are operated, for example, using a compressed-air oil atomizer nozzle known from EP-A-0 566 855 or EP-A-0 731 315. In oil-operated heating systems, the heating oil to be combusted is sprayed at a pressure of several bar (approximately 5 bar) through a compressed-air atomizer nozzle into the burner chamber and atomized. To prevent the heating oil from dribbling due to the high pressure when the burner is shut down, in the above-mentioned publications, a diaphragm having a closing piston pre-tensioned by a compression spring (EP-A-0 566 855) or a diaphragm clamped between two springs (EP-A-0 731 315) is provided.

These known devices are especially implemented for heating oil, which must maintain special qualities because of the environmental technology guidelines. In particular, it is not possible to combust other vegetable oils such as canola oil or also fat using such a device.

SUMMARY OF THE INVENTION

It is the object of the present invention to improve such a device for combusting liquid fuels in such a way that it is possible to combust types of oils and fats other than heating oil.

This object is achieved by a device having the features of claim 1 and by a method having the features of claim 6.

The essential finding of the present invention is that, in contrast to the typical compressed-air atomizer nozzles, the compressed air is used as an energy carrier and control medium for the valve configuration. The supply of liquid or powdered fuel may thus be performed at a lower pressure and thus a very precise control of the valve configuration may be achieved. The compressed air used for the control suctions the liquid or powdered fuel because of the partial vacuum, so that outstanding mixing and/or atomization of the fuel with the compressed air already occurs in the mixing chamber.

Using the device according to the invention, various types of fuel and qualities of fuel may be combusted without any parts having to be replaced. Fuels having an admixture of up to 20% water may also be combusted without problems. If the compressed air is replaced by pure oxygen, a part of the water entrained as mist is decomposed and combusted, which results in a higher flame temperature.

Further advantages of the invention result from the dependent claims and from the following description, in which the invention is explained in greater detail on the basis of an exemplary embodiment illustrated in the schematic drawings. In the figures:

FIG. 1 shows a combustion device having an atomizer nozzle, a pre-heater, and a compressed air supply,

FIG. 2 shows the atomizer nozzle of FIG. 1 in greater detail, clamped in a nozzle assembly having a sheath, shortly before the valve is opened,

FIG. 3 shows the same atomizer nozzle of FIG. 2 having closed valve,

FIG. 4 shows the same atomizer nozzle of FIG. 2 with open valve,

FIG. 5 shows the same atomizer nozzle of FIG. 2 after the valve is closed,

FIG. 6 shows a cross-section in the longitudinal direction through a flame pipe,

FIG. 7 shows a cross-section in the transverse direction through the flame pipe of FIG. 6,

FIG. 8 shows a pneumatic-hydraulic control scheme for the controller of the combustion device, and

FIG. 9 shows a variant of the atomizer nozzle.

DESCRIPTION OF THE INVENTION

The same reference numerals have been used in each case for the same elements in the figures and initial explanations relate to all figures, if not otherwise expressly noted.

FIG. 1 shows a combustion device 1 having an atomizer nozzle 2, a sheath 3 having a compressed air connection 4, and an oil preheater 5. The sheath 3 essentially encloses the oil preheater 5, so that the compressed air which flows through the sheath 3 is simultaneously preheated by the preheater 5 to approximately the same temperature as the oil. The oil preheater 5 comprises a shaft 6 having a resistance heater 7 wound thereon and a plastic housing 8 for the terminals 9 for the heating coil. A fuel supply pipe 10 is mechanically connected to the shaft 6. A connection sleeve 12 is screwed onto the oil preheater 5, which carries the atomizer nozzle 2 on the other side using a screwed-on fastening sleeve 13. The connection sleeve 12 is provided with a so-called volustat throttle 14 having a small flow-through hole 15, in which the fuel pressure and the flow rate are decreased. Furthermore, a large-mesh filter 16 made of sintered metal is attached in front of the volustat throttle 14. The pumping pressure of the oil is dissipated with the aid of the throttle 14 and simultaneously the desired oil quantity is metered as a function of the pumping pressure depending on the power demand. The throttle 14 may also be installed in the nozzle assembly directly after the oil pump.

Further details of the atomizer nozzle 2 are shown and explained on the basis of FIGS. 2 and 3. An axially-symmetric receptacle chamber 21 is formed between the fastening sleeve 13 and the screwed-in nozzle body 20 of atomizer nozzle 2. Viewed from this receptacle chamber 21, an axial pocket hole 22 is shaped into the nozzle body 20, which tapers at its base in a truncated cone up to a nozzle opening 23 of the nozzle body 20. An axially-symmetric insert 24 is screwed into this pocket hole 22 of the nozzle body 20. The rear end of the insert 24 facing away from the nozzle opening 23 has a front sleeve section 25, which is inserted into the connection sleeve 12 implemented as the nozzle assembly and guided sealed therein. The seal is produced by an O-ring 26. This O-ring 26 presses on the other side against the inner wall of an axial sliding chamber 27 of the connection sleeve 12, in which a supply line 28 for the liquid or powdered fuel opens.

Compressed air—shown by arrows 30—is supplied in the receptacle chamber 21 of the fastening sleeve 13. The receptacle chamber 21 then passes via air supply lines or holes 50—see below—into an essentially cylindrical ring gap 31, which is formed between the insert 24 and the nozzle body 20, and which in turn passes because of the tapering in a truncated cone of the pocket hole 22 toward the nozzle opening 23 into a gap 32 essentially in the form of a truncated cone. The cylindrical ring gap 31 arises in that the diameter of the pocket hole 22 is somewhat greater than the diameter of the forward sleeve section 25 of the insert 24 facing toward the nozzle opening 23. The gap 32 in the form of a truncated cone arises through a corresponding axial offset between the base in the form of a truncated cone of the pocket hole 22 and a front part of an axially-symmetric clamping element 33, situated on the insert 24, which is described below. The base of the pocket hole 22 is covered by guide channels—not shown here—running approximately tangentially to the nozzle opening 23, as shown in FIGS. 2 and 3 of EP-A-0 566 855. The cylindrical ring gap 31 and the gap 32 in the form of a truncated cone thus together form an axially-symmetric intermediate space between the insert 24 and the nozzle body 20.

Viewed from the forward sleeve section 25, a continuous axial hole 36 is shaped into a metal part 34 and, adjoining thereto, into the rear sleeve section 35 of the insert 24, which is connected to the rear to the sliding chamber 27 and to the supply line 28 for oil. This axial hole 36 tapers at its other end, the end being enclosed by a ring wall 37. The upper edge of the ring wall 37 is in the same plane as a ring shoulder 42 of the forward sleeve section 25, so that a ring groove 38 implemented as a mixing chamber is implemented on the other side of the ring wall 37, which is connected via radial holes or radial channels 39 to the cylindrical ring gap 31.

A disc-shaped diaphragm 41 lies on the upper edge of the ring wall 37, which overlaps the ring groove 38 and has its edge resting on the ring shoulder 42 of the forward sleeve section 25. The diaphragm 41 is clamped on its edge on this ring shoulder 42 using a clamping element 33. This clamping element 33 is pushed into the forward sleeve section 25 using a press fit and thus fastened. This clamping element 33 is shaped in the form of a truncated cone toward the nozzle opening 23 in the area of the base of the pocket hole 22 of the nozzle body 20, to form the gap 32 in the form of a truncated cone of the above-mentioned axially-symmetric intermediate space.

A pocket hole 43 is shaped into the clamping element 33, in which a closing piston 44 is retained so it slides. This closing piston 44 presses against the diaphragm 41 using a compression spring 45. The compression spring 45 is supported on one side against the funnel-shaped floor of a pocket hole 46 in the closing piston 44 and on the other side against a funnel-shaped floor of the pocket hole 43. In addition, a relief hole 48 leads out of this hole to the gap 32 in the form of a truncated cone, which is situated axially to the diametrically opposite nozzle opening 23 of the nozzle body 20.

Furthermore, holes 50 implemented as air supply lines are provided in the middle part 34 of the insert 24, which lead from the receptacle chamber 21 to the ring groove 38. These holes 50 connect the receptacle chamber 21 to the ring groove 38, so that the compressed air 30 is directed directly onto the diaphragm 41.

The atomizer nozzle 2 is shown in FIGS. 4 and 5 having the valve or the diaphragm 41 in the open state and in the closed state, respectively.

A special flame pipe 55 is shown in FIGS. 6 and 7, which is fastened onto a typical fastening pipe (not shown here) using screws in the threaded holes 56. The combustion device shown in FIG. 1 has a typical mixing system—not shown further here—on the front side having ignition electrodes and is mounted having the atomizer nozzle 2 at the intake of the flame pipe 55. As is obvious from FIGS. 6 and 7, the flame pipe 55 is largely tapered in the intake area 57 and is only screwed onto the fastening pipe at the protrusions 58, which correspond to the internal diameter of the fastening pipe, so that the heat in the flame pipe is only transferred in a limited way to the fastening pipe. The flame pipe 55 is preferably produced from a ceramic material. Hot exhaust gases are supplied once again to the flame by the so-called recirculation gap between the flame pipe 55 and the fastening pipe. These exhaust gases are sucked back from the outside at the flame pipe 55 through the recirculation gap. More optimum exhaust gas values are achieved by the entrained gases.

The flame pipe 55 may also be produced from metal and be internally lined with a felt made of fireproof ceramic fibers or with a vacuum-compressed and/or drawn internal pipe made of ceramic fibers. The sheath 3 (see FIG. 1) is preferably also covered on the flame side with such a felt. This lining or felt prevents the spray mist from condensing on the relatively cold surface of the flame pipe 55 in the cold state. Furthermore, the felt insulates the flame pipe 55 and the sheath 3 from the hot flame, so that less material aging results.

FIG. 8 shows a pneumatic-hydraulic control scheme for the combustion device 1 according to the invention. Regulating electronics 60 having a heater 61, a feeler element 62, and a thermostat 63 are provided in the retainer of the compressed air atomizer nozzle 1. The thermostat 63 is connected to a time delay 64. A double diaphragm compressor 66 on one hand and an oil pump 67 on the other hand are driven using a motor M. A solenoid valve 69 and a compressed air monitor 70 and a compressed air regulator 71 are provided in the compressed air supply line 68. A solenoid valve 73 is provided in the oil supply line 72.

FIG. 9 shows a variant of the atomizer nozzle 2. Identical elements are identified using identical reference numerals and are not explained further here. An axially-symmetric clamping element 33′ is fastened in the pocket hole 22′ of the nozzle body 20′, which, with the base of the pocket hole 22′, forms a gap 32′ in the form of a truncated cone having guide channels running tangentially to the nozzle opening 23′. The closing piston 44′ is now implemented having a peripheral ring groove 82, in which an O-ring 83 is inserted, which completely seals the gap between closing piston 44′ and clamping element 33′. Instead of the diaphragm 41 of the embodiment of FIG. 1, a sealing disc 84 made of rubber is now inserted in a recess 85 in the form of a circular disc, which forms the valve. Holes 50′ implemented as air supply lines and situated parallel to the axial hole 36′, which lead to the ring groove 38′, are now provided in the middle part 34′ of the insert 24′. This ring groove 38′ passes into a ring groove 86 in the form of a truncated cone toward the center, which is sealed by the sealing disc 84. This sealing disc 84 simultaneously seals the axial hole 36′, which is used for the oil supply.

The mode of operation of the combustion device 1 may be explained as follows on the basis of the figures:

When the burner receives a pulse to start the combustion procedure, fuel is firstly heated in the nozzle assembly using oil preheater up to a temperature of at most 80° C., to prevent the oil from coking. After release by the thermostat 63, the time relay 64 is activated using a settable delay time. For easily ignitable oils such as petroleum, the delay time may be set to zero, so that the burner starts immediately. For less flammable fuels such as vegetable oils, the delay time may be set to several minutes so that the generated heat may propagate over the volustat throttle 14 up to the nozzle 2. After the set time has passed, the burner is started.

During the preliminary flushing time of the burner, the compressed air is built up using the double diaphragm compressor 66 and is then available at the solenoid valve 69. When the control mechanism of the burner gives the start release, the solenoid valve 69 is opened. The compressed air then flows in the direction of nozzle 2. In order that the compressed air does not cool down the fuel to be atomized, it is guided on the oil preheater 5 in the sheath 3. The preheated air is available at the valve or at the diaphragm 41 of the nozzle 2. As soon as the pressure of the compressed air is greater than the counter pressure exerted by the closing piston 44 and the compression spring 45 on the diaphragm 41, the valve or the diaphragm 41 is opened and the oil flows into the ring groove 38 implemented as a mixing chamber, so that air and oil are mixed and the oil is entrained by the outflowing air. The partial vacuum generated at the nozzle opening 23 also additionally acts on the closing piston 44 and thus on the diaphragm 41. The fuel flowing out of the valve is entrained by the air flowing past and caused to rotate shortly before the nozzle outlet by tangential channels (as also known from FIGS. 2 and 3 of EP-A-0 566 855). An extremely fine fuel mist, which is similar to a gas, arises through this rotation and the forward flow of the fuel-air mixture as it leaves the nozzle opening 23. Due to this fine misting or gasification, the poorly flammable mixture has become easier to ignite. The ignited mixture thus burns better, because the flame is not only supplied with air from the outside, but rather the compressed air which is used for atomization now also reacts from the flame middle toward the outside, which significantly accelerates the combustion. The combustion preferably occurs in a flame pipe 55, which advantageously comprises a ceramic. The exhaust gases exiting from the flame pipe 55 have no unburned residues and thus do not require any post-combustion.

It is obvious to one skilled in the art that the mode of operation of the atomizer nozzle according to FIG. 9 is similar. The closing piston 44′ is also moved by the partial vacuum toward the nozzle opening 23′ and the valve is thus opened.

The flame pipe 55 may be set using an adjustable recirculation gap on the fastening pipe, by which the combustion may be additionally optimized. 

1. A device for combusting a liquid or powdered fuel having an atomizer nozzle (2), which has a valve configuration (41) for controlling the supply of the fuel, a compressed air connection (4), a mixing chamber (38) for mixing the fuel with compressed air, and a nozzle opening (23) for atomizing a mist of fuel in compressed air, having a supply line (28) for the fuel and having an apparatus (5) for preheating the fuel to a predetermined temperature, which is provided in a nozzle assembly surrounding the nozzle (2), characterized in that air channels are provided in a sheath (3) enclosing the preheating apparatus (5) and a fastening sleeve (13) having connection channels adjoining the air channels, the sheath (3) forming a ring gap (21) for the supply and heating of the compressed air with the nozzle assembly (12) of the atomizer nozzle (2), and the air supply lines (50) originating from the ring gap (21) being provided in the nozzle body (20) in such a way that the valve configuration (41) is activatable by the compressed air.
 2. The device according to claim 1, characterized in that the valve configuration is formed by a clamped diaphragm (41) or by a compression disk (84), and the nozzle (2) has an axial fuel channel (36) terminated by the diaphragm, and the air supply lines (50) radially enclose the fuel channel and encounter the diaphragm or the compression disk.
 3. The device according to claim 2, characterized in that at least two air supply lines (50) are provided, which are situated at an equal distance diametrically opposite to the fuel channel.
 4. The device according to claim 2, characterized in that the mixing chamber is formed by a ring groove (38) enclosing the fuel channel (36), into which the air supply lines (50) open.
 5. The device according to claim 1, characterized in that the nozzle assembly is formed by a connection sleeve (12) having a throttle (14) for decreasing the flow rate and the fuel pressure.
 6. The device according to claim 5, characterized in that the connection sleeve (12) is fastened liquid-tight to the transition sleeve (13) and the transition sleeve (13) is fastened liquid-tight to the nozzle body (2).
 7. The device according to claim 6, characterized in that the connection sleeve (12) is fastened to the transition sleeve (13) using a screw connection and the transition sleeve (13) is fastened to the nozzle body (20) using a screw connection.
 8. The device according to claim 1, characterized in that a flame pipe (55), preferably made of a ceramic or internally lined with ceramic fibers, is provided at the outlet of the atomizing nozzle (2), which is essentially tapered at the rear end facing toward the atomizing nozzle (2), so that a recirculation gap is formed between a fastening pipe and the flame pipe (55).
 9. The device according to claim 1, characterized in that the solenoid valve (73) is provided before the compressed air connection (4), which is switched using a time delay relay (64) via a burner controller, to heat the fuel during a predetermined time and, after passage of this time, to open the valve configuration (41) and start the burning procedure.
 10. A method for combusting a fuel using a device according to claim 1, characterized in that a liquid or powdered fuel is preheated in a supply line (28) using a preheating apparatus (5) and supplied to a valve configuration (41), compressed air is preheated in direct proximity to the preheating apparatus (5) and supplied via air supply lines (50) in the nozzle body (20) to the valve configuration (41) in such a way that the compressed air activates the valve configuration (41).
 11. The method according to claim 10, characterized in that the compressed air opens the valve configuration (41) after a time delay to preheat the fuel during a predetermined time using the preheating apparatus (5) and to start the burning procedure after passage of this predetermined time. 